Upgrading of bio-oil using synthesis gas

ABSTRACT

A method for producing biofuel and other hydrocarbons from bio-oil is disclosed. The method does not require the use of hydrogen derived from fossil fuel.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/697,918 by Steele, et al., filed Sep. 7, 2012, which is incorporatedherein by reference in entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under 0221966 awarded bythe National Institute of Food and Agriculture (NIFA) andDE-FG36-06GO86025 the U.S. Department of Energy. The government hascertain rights in the invention.

FIELD OF THE INVENTION

The present invention is generally directed toward a method forproducing fuel from bio-oil.

BACKGROUND OF THE INVENTION

Fuels from biomass have environmental advantages. The plant growthrequired to produce the biomass feedstock consumes carbon dioxideoffsetting the carbon dioxide produced when the fuel is ultimatelycombusted. Carbon dioxide is a greenhouse gas generally recognized to bethe cause of adverse climate effects. A zero carbon footprint iscurrently not economically feasible with fossil fuels. Another advantageof biofuels is that it reduces our reliance on foreign oil. Aneconomically feasible biofuel is considered important to the US energysecurity particularly in the light of the current unstable politicalsituation in many countries that supplies the US with its fuel.

One of the current drawbacks of bio-oil is that when it is produced itis unstable. The raw bio-oil must be treated to improve its stabilityand its suitability as a fuel. Treatment with hydrogen is routinely doneto hydrogenate and hydrodeoxygenate thus improving heating value andstability while reducing oxygen content of the fuel. This treatment iscommonly performed in the presence of a catalyst. The problem with thistreatment is that, in the US, hydrogen is primarily produced from thesteam reforming of natural gas—a fossil fuel. In our opinion, consuminga large quantity of fossil fuel to make a biofuel is counterproductive.

Biomass liquefaction to bio-oil leaves far more of the total caloricvalue of the starting biomass in the product liquid (bio-oil) thangasification to syngas followed by Fischer Tropsch (FT) synthesis offuels. Thus, bio-oil's potential for fuel production is far greater thanthat of FT from bio-gasification Thus, there is a need in the art foralternative processes or methods for producing fuel and otherhydrocarbons from bio-oil that does not require hydrogen derived fromfossil fuels.

SUMMARY OF THE INVENTION

In a first object of the invention, we disclose a method for upgradingbio-oil into hydrocarbons and other fuel products that utilizessynthesis gas, or syngas, as a source of hydrogen from gasification ofbiomass or other sources to complete.

In a second object of the invention, we disclose a method for upgradingbio-oil into hydrocarbons and other fuel products that utilizes thewater gas shift reaction (WGS) to provide hydrogen for the upgradingprocess.

We also disclose a method for upgrading bio-oil into hydrocarbons andother fuel products that utilizes syngas or WGS as a source for hydrogento facilitate the upgrading process.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention will become apparent by reference tothe detailed description of preferred embodiments when considered inconjunction with the drawings:

FIG. 1 depicts a diagram of a batch reactor.

FIG. 2 depicts a diagram of a flow system

FIG. 3 depicts a diagram of batch reactor with olefin or alcohol.

FIG. 4 depicts a another diagram of a reactor with olefin or alcohol.

DESCRIPTION OF THE TECHNOLOGY

The following detailed description is presented to enable any personskilled in the art to make and use the invention. For purposes ofexplanation, specific details are set forth to provide a thoroughunderstanding of the present invention. However, it will be apparent toone skilled in the art that these specific details are not required topractice the invention. Descriptions of specific applications areprovided only as representative examples. Various modifications to thepreferred embodiments will be readily apparent to one skilled in theart, and the general principles defined herein may be applied to otherembodiments and applications without departing from the scope of theinvention. The present invention is not intended to be limited to theembodiments shown, but is to be accorded the widest possible scopeconsistent with the principles and features disclosed herein.

The technology described herein consists of a hydrodeoxygenation processwhere the hydrogen, from the synthesis gas, reacts with the bio-oil inthe presence of a catalyst and removes oxygen atoms. With this processwe see improvements in heating value, acidity, stability andcompatibility with other fuels. In addition the CO (also from thesynthesis gas) reacts with water present in the bio-oil to produceadditional hydrogen and easily removed carbon dioxide. This helps tolower bio-oil water content.

The preparation of the catalyst used in this process is as follows. Acopper based low temperature catalyst useful for promoting the water gasshift is acquired and used as received. HDO catalysts is prepared using5 wt % metal loading with a ZSM-5 supporting material via incipientwetness impregnation method then calcined for 3 h at 500° C. andpelletized.

Synthesis gas (50/50 CO/H₂) or biosynthesis gas is used to first purgeand then pressurized the reactor. The pressure ranged from 300 to 1200PSI and at temperatures between 200 and 350° C. The catalyst, liquidproduct and gas are separated and analyzed while any char is discarded.

The following exemplary embodiments depicts methods that may be used.The numbers in each drawing are only illustrative and correspond only tothe figure shown.

As will be appreciated from FIG. 1, raw bio-oil from bio-oil storagetank 1 is transferred to a stirred tank 3 which contains a dual catalystsystem including a WGS catalyst and a hydrodeoxygenation (HDO) catalyst.Synthesis gas from the synthesis gas storage tank 2 is transferred totank 3. The reactor is then mixed and heated resulting in upgradedbio-oil. The upgraded bio-oil is then transferred to an upgraded bio-oilstorage tank 4 for subsequent shipment.

In a flow system embodiment shown in FIG. 2, raw bio-oil from bio-oilstorage tank 1 and synthesis gas from synthesis gas storage tank 2 aretransferred to a flow reactor 3 which contains a dual catalyst systemincluding a WGS catalyst and a HDO catalyst. The reactor is heated to afixed temperature between 200 and 350° C. while maintaining a constantsynthesis gas pressure and reactant flows from tanks 1 and 2. As thebio-oil travels through the reactor upgraded bio-oil is produced.Bio-oil flow through the system will depend on reactor diameter,catalyst packing length and reaction temperature. The upgraded bio-oilis then transferred to an upgraded bio-oil storage tank 4 for subsequentshipment.

FIG. 3 depicts an embodiment of a batch reactor that uses alcohol. Aswill be appreciated from figure, raw bio-oil from bio-oil storage tank1, alcohol from storage tank 2 and synthesis gas from synthesis gasstorage tank 3 are transferred to a stirred tank 4 which contains a dualcatalyst system including a WGS catalyst and a HDO catalyst. The reactoris then mixed and heated resulting in upgraded bio-oil. The upgradedbio-oil is then transferred to an upgraded bio-oil storage tank 5 forsubsequent shipment. In an alternative embodiment, the alcohol instorage tank 2 is replaced with an olefin.

As will be appreciated from the embodiment depicted in FIG. 4, rawbio-oil from bio-oil storage tank 1, alcohol from storage tank 2 andsynthesis gas from synthesis gas storage tank 3 are transferred to aflow reactor 4 which contains a dual catalyst system including a WGScatalyst and a HDO catalyst. The reactor is heated to a fixedtemperature between 200 and 350° C. while maintaining a constantsynthesis gas pressure and reactant flows from tanks 1 and 2. As thebio-oil travels through the reactor upgraded bio-oil is produced.Bio-oil flow through the system will depend on reactor diameter,catalyst packing length and reaction temperature. The upgraded bio-oilis then transferred to an upgraded bio-oil storage tank 4 for subsequentshipment. An additional embodiment would be to replace the alcohol withan olefin in storage tank 2.

It is expected that upgrading bio-oil with syngas has many advantagesover pure hydrogen: 1) Syngas can be produced from the same renewablefeedstock used to produce the bio-oil. 2) It is a renewable source ofhydrogen—hydrogen treatment is a proven step in stabilizing andimproving fuel quality. 3) Particularly exciting is the presence ofcarbon monoxide in syngas.

Theory and Laboratory Results

Under the correct combination of reaction conditions and catalyst thecarbon monoxide can undergo the water gas shift reaction:

CO+H₂O→CO₂+H₂

The use of the water gas shift reaction provides a way to remove waterpresent in the bio-oil. The CO in syn-gas reacts with water to make CO₂(which is a gaseous product that separates) and hydrogen (which thenproceeds to be consumed as the upgrading occurs). Therefore, syn-gasrefining provides a unique way to dewater the bio-oil while providingadditional hydrogen.

The Invention

This invention utilizes pressurized syngas which can be produced frombiomass to replace the hydrogen produced by steam reforming of naturalgas. Hydroprocessing of bio-oil is currently performed by applyingpressurized hydrogen in the presence of a catalyst at appropriatepressure and temperature. We have preliminary results indicatingsignificant hydroprocessing effectiveness utilizing pressurized syngasfrom gasification of biomass. However, the syngas can come from anysource and preserve the novelty of the invention.

This invention also employs the water gas shift reaction (WGS) toproduce additional hydrogen, above that contained in the syngas itself,for hydroprocessing upgrading of the bio-oil to hydrocarbons. The WGSequilibrium consumes CO abundant (˜23%) in the syngas to generate H₂via: H₂O+CO=H₂+CO₂. By consuming the H₂ in upgrading, the WGSequilibrium will be driven toward completion. This means that waterremoval can continue to occur and the decrease of water will not beequilibrium limited. The WGS approach is expected to remove much of thewater present in the bio-oil which is a primary objective of bio-oilupgrading.

Both low temperature and high temperature WGS catalysts are well known.Low temperature catalysts can be employed in the hydrotreating stagewhere temperatures are maintained below 300° C. High temperature WGScatalysts can then be applied during the 2^(nd) stage hydrocracking thatrequires temperatures up to 500° C. Some well-known low temperature WGScatalysts useful in the temperature range of 180 to 350° C. include thefollowing: CuO—ZnO, Cu—(La)O, Fe₂O₃/Cr₂O₃, CuO—ZnO—Al₂O₃, CuO—ZnO—Cr₂O₃,Cu/CeO₂ and Ni/CeO₂. Our invention is not limited to these catalysts andany effective WGS catalyst may be applied to preserve the novelty of ourinvention.

A heterogeneous acid catalyst is required to catalyze thehydroprocessing reactions. The catalyst type may include at least one ormore metals selected from nickel (Ni), chromium (Cr), molybdenum (Mo),and tungsten (W), cobalt (Co), rhodium (Rh), iridium (Ir), ruthenium(Ru), rhenium (Re), platinum (Pt), and palladium (Pd) supported on alltypes of alumina, silica, silica-alumina, titania, zirconia and alltypes of zeolites. In some cases acids are also used as catalysts suchas sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid.The heterogeneous catalyst may have WGS reaction capabilities to improvethe production of hydrogen from WGS catalyst alone.

A novel aspect of our approach is the potential utilization of a dualcatalyst combining a WGS catalyst with a hydroprocessing catalyst. Thecombination of these catalysts has the potential to increase hydrogenproduction significantly above that possible with the use of eachcatalyst type alone. The hydroprocessing step produces a high percentageof water. The WGS reaction will use the water produced from thehydroprocessing step to increase hydrogen production.

The terms “comprising,” “including,” and “having,” as used in the claimsand specification herein, shall be considered as indicating an opengroup that may include other elements not specified. The terms “a,”“an,” and the singular forms of words shall be taken to include theplural form of the same words, such that the terms mean that one or moreof something is provided. The term “one” or “single” may be used toindicate that one and only one of something is intended. Similarly,other specific integer values, such as “two,” may be used when aspecific number of things is intended. The terms “preferably,”“preferred,” “prefer,” “optionally,” “may,” and similar terms are usedto indicate that an item, condition or step being referred to is anoptional (not required) feature of the invention.

The invention has been described with reference to various specific andpreferred embodiments and techniques. However, it should be understoodthat many variations and modifications may be made while remainingwithin the spirit and scope of the invention. It will be apparent to oneof ordinary skill in the art that methods, devices, device elements,materials, procedures and techniques other than those specificallydescribed herein can be applied to the practice of the invention asbroadly disclosed herein without resort to undue experimentation. Allart-known functional equivalents of methods, devices, device elements,materials, procedures and techniques described herein are intended to beencompassed by this invention. Whenever a range is disclosed, allsubranges and individual values are intended to be encompassed. Thisinvention is not to be limited by the embodiments disclosed, includingany shown in the drawings or exemplified in the specification, which aregiven by way of example and not of limitation.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

All references throughout this application, for example patent documentsincluding issued or granted patents or equivalents, patent applicationpublications, and non-patent literature documents or other sourcematerial, are hereby incorporated by reference herein in theirentireties, as though individually incorporated by reference, to theextent each reference is at least partially not inconsistent with thedisclosure in the present application (for example, a reference that ispartially inconsistent is incorporated by reference except for thepartially inconsistent portion of the reference).

We claim:
 1. A method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes synthesis gas, or syngas, as a source of hydrogen from gasification of biomass or other sources to complete.
 2. A method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes the water gas shift reaction (WGS) to provide hydrogen for the upgrading process.
 3. A method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes syngas or WGS as a source for hydrogen to facilitate the upgrading process.
 4. A method for upgrading bio-oil into hydrocarbons and other fuel products that utilizes syngas or WGS as a source for hydrogen and a catalyst composed of CuO—ZnO, Cu—(La)O, Fe₂O₃/Cr₂O₃, CuO—ZnO—Al₂O₃, CuO—ZnO—Cr₂O₃, Cu/CeO₂, Ni/CeO₂, and/or other catalysts useful for the upgrading process including those that contain at least one or more of the following metals Ni, Cr, Mo, W, Co, Rh, Ir, Ru, Re, Pt, and Pd along with a suitable support material. 